M&S says

For a pack of knickers that are designed to last, these feature a cotton rich fabric that has a touch of Lycra® for added support and a great fit that stays comfy. These midi knickers have our StayNEW™ finish on the fabric to help prevent colour loss and bobbling over time, keeping them like new for longer.

Style

Care and Composition

35 days to return
You may return unused products within 35 days of purchase with a valid parcel summary document. Your items don't need to be in the original box or bag as long as they're securely packaged.

How to return
Simply use our returns portal to print a returns label and returns note. You will then be able to return all or part of your order at your own cost through your preferred carrier. To create a returns label, visit our returns portal select this option and follow the instructions.